Rectifier-protective system



Oct. 11 1927.

. v D. G. LITTLE ET AL RECTIIFIIE'R PROTECTIVE SYSTEM Filed April 15. 1925 INVENTORS A'TToRNEY Doncfld G. Li'H'le and Robert L.Dcvis.

WITNESSES:

i ingly steep wave front.

Patented Oct; 11, 1927.

UNITED STATES PATENT OFFICE.

DONALD G. LITTLE AND ROBERT L. DAVIS, OEWILKINSBURG, PENNSYLVANIA, AS-

SIGNORS TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A COR- PORATION OF PENNSYLVANIA.

RECTIFIER-PROTECTIVE SYSTEM.

Application filed April 15, 1925. Serial No. 23,428.

Our invention relates to protective devices for thermionic discharge devices and particularly for excess voltage discharge means for such devices.

6 An object of our invention is to construct a protective system for vacuum tube rectifiers. I

Another object of our invention is to con struct an excess voltage discharge device for 10 hot cathode rectifiers whereby excess voltages will be drained ofi' without damage to the connected apparatus.

In the operation of high power radio sending apparatus containing large power triodes it has been 'found desirable to supply the necessary veryhigh voltage direct current from thermionic rectifier devices which frequently are substantally similar in general construction to triodes with the third electrode omitted.

In the operation of these systems difiiculty is experienced because of injury to connected electromagnetic opparatus such as the supply transformers by failure of the $5 insulation therein. Investigation has shown that the cause for this injury is the development of impulse currents or surges in the rectifier apparatus. Under certain operating conditions, it, is possible for the hot cathode to make momentary contact with the anode structure, thereby short circuiting its connected transformer for a short period of time. This period, while of brief duration, gives rise to electrical disturbances for a very short period and having a correspond- It has also been found that rectifier'devices of the type described sometimes contain slightly more vapor than is anticipated,

40 especially toward the end of their effective life. The presence of this vapor occasionally permits ionization phenomena to occur which also result in momentary current'disturbances resulting in electrical surges of extremely steep wave front.

These disturbances may be conveyed to the supply transformer or to the steadyin'g inductance. Both of these pieces of apparatus are constructed to have very high impedances, both total and per turn, and in consequence the steep wave fronts develop very high potentials in the first few turns which may injure the insulation, resulting proper angle.

of the sphere gap, resistor and inductor are shown on the drawing. The insulating plate 18, is mounted-upon an insulator 19, supportedlby a frame work 21. One of the spheres of the gap 14 is carried by a conducting rod 22, the lower end of which is attached to the plate 18, and connected to a terminal of the inductor 12, the other end of which is fastened to the insulator 23- and connected to the anode of the rectifier 6.

The second sphere of the gap 14 is attached to a rod 24 which is mounted upon an insulator 25, carried by another. portion of the frame work 21. A spring clip 26 is attached to the other end of the rod 24:. Another. spring clip 27 is attached to the grounded frame work 21. The clips 26 and 27 support the resistor 15. The portions of rods 22 and 24 which extend upward from the spheres of the gap 14 are adapted to function as additional arc extinguishing means by drawing the are out to a greater length.

The plate 18 of insulation is supported at the lower end by the insulator 19. At its upper end it is braced by the member 22 which supports one terminal of the gap 14. The member 22 serves, therefore, as a o0nductorbetween-the coil 12 and the anode of the tube 6 and as a mechanical brace for the plate 18, has the still further function that it constitutes one of the horns of the spark gap. It will be seen that a double curvature is introduced between the horizontal and the vertical portions of member 22, in order to provideahorn disposed at a In the operation of'our device, thedevelopment of impulse currents, surges and steep wave front currents by various means, as above descrlbed, create high potentlals across the gaps 14 and 17. The separation between the respective spheres in these gaps is of such magnitude that ordinary potentials do not cause a break down of the gap and passage of currents, but the separation is such that a higher voltage will cause current to flow across the gap and through the resistor for the equalization of the surge potentials. Power current from the secondary of the transformer 9 is, however, prevented from flowing by the resistors 1-5 and 18 which limit the current flow to such avalue that the spheres of the gap are not heated to a point where a power are will continue to flow after the cessation of the application of the excess potential.

By this means we have been enabled to provide a very satisfactory degree of protection for the connected electromagnetic apparatus combined with a high voltage thermionic rectifier device, thereby materially reducing the cost of operation from damage to apparatus and materially increasing the certainty of continuous operation.

While we have shown but a single embodiment of our invention in the accompanyng drawing, it is capable of various changes and modifications therefrom without departing from the spirit thereof, and it is desired therefore, that only such limitations shall be placed thereon as are imposed by the prior art or indicated in the appended claim.

We claim as our invention:

In a safety device for vacuum tube apparatus, a' spark gap, a Vertically disposed supporting member of insulation for one side of said gap, a conductor extending from said spark gap to the anode of a tube, said conductor being secured to the upper end of said insulating supporting member whereby the conductor constitutes a brace for said supporting member, said conductor having a circumflex bend adjacent the spark gapwhereby a portion of the conductor constitutes a horn ofv the spark gap.

In testimony whereof, we have hereunto subscribed our names this 6th day of April,

DONALD G. LITTLE. ROBERT L. DAVIS. 

